Pulp density indicator



Ap 1951 w. WRAITH,'JR 2,550,031

PULP DENSITY INDICATOR Filed Oct. 23, 1947 ATTORNEYS INVENTOR WlLLlAM WRAITH JR.

BY (Zn/11 W um/W Patented Apr. 24, 1951 PULP DENSITY INDICATOR William Wraith, Jr., Cananea, Mexico, assignor to The Cananea Consolidated Copper Company, S. A., a'corporation of Mexico Application October 23, 1947, Serial No. 781,574

3 Claims.

This invention relates to apparatus for indicating the density of aqueous pulps, and has for its principal object the provision of improved pulp-density indicating apparatus that is es-. pecially well suited for indicating the density of ore pulps in mineral concentration mills. The new apparatus comprises an improved hydrometer vessel especially designed to insure maintenance therein of a truly. representative and substantially quiescent body of the pulp whose density is to be indicated. A hydrometer float positioned in the vessel is arranged to indicate the density of the pulp.

In the concentration of minerals by the froth flotation process, the ore is ground and is carried through the flotationprocess in an aqueous pulp. Accurate control of the density of the pulp at various stages of the process is important for achieving optimum and mosteconomical grinding and concentration. Satisfactory devices for indicating or controlling the pulp density at some stages of the ore pulp, circuit have been available for many years, but, on the other hand, it has proved very difficult to provide reliable, accurate and rugged pulp density indicating apparatus for other stages of the circuit. For example, the pulp,

density of the overflow from classifiers operating in closed circuit with ball mills in a copper ore concentrator plant, which overflow forms the feed to the flotation cells, should be accurately known and controlled at all times. However, no thor oughly satisfactory apparatus suitable for installation in the overflow stream of pulp from the classifier has been available heretofore. The volume of pulp in the overflow from such classifier is large, so it is not feasible to pass it all through a pulp density indicator. The samples taken for making the density measurement must, however, be truly representative of the entire volume of pulp. Furthermore, density measurements are best made on a substantially quiescent body of the pulp. The difficulty heretofore experienced in collecting and maintaining a truly representative and substantially quiescent body of pulp, for density indicating purposes, from a large volume of an overflowing pulp stream has been a major factor in the lack heretofore of a satisfactory pulp density indicator for such stages in a concentrator plant pulp circuit as the ball-mill classifier overflow.

The present invention provides an improved pulp density indicator that has proved very satisfactory for providing a continuous indication of the density of an aqueous pulp as it overflows from one container to another (e. g. from a classifier or launder into another launder). The improved pulp density indicator comprises an indicator vessel in the form of an inverted cone having an inlet opening in its wall, a discharge opening in its downwardly pointing apex, and an overflow lip about its upper edge. The vessel is supplied with pulp through a feed conduit mounted on the conical side wall, with the lower end of the conduit communicating with the interior of the vessel through the inlet opening. The upper end of the conduit terminates, near the upper edge of the vessel, in a feed lip that can be interposed in the path of an overflowing stream of pulp, so as to divert a part of the pulp stream through the feed conduit and deliver it into the vessel. A considerable part of the pulp is discharged from the vessel by flowing down through the discharge opening at its bottom, but sufficient pulp enters the vessel so that a part must flow upwardly and overflow across the overflow lip. This portion of the pulp forms a substantially quiescent but continuously changing body of the pulp that is truly representative of the pulp stream in which the feed lip of the feed conduit is interposed. To insurethat this body remains substantially undisturbed and quiescent, a baffle extends upwardly from between the feed conduit feed lip and the vessel overflow lip. The baffle shields the body of pulp in the vessel from agitation by splashing of the pulp stream flowing into the feed conduit.

A hydrometer float, immersed in the quiescent body of pulp in the vessel, is connected to a pulp density indicating lever. The lever may be provided with a pointer which traverses a pulp den sity scale, to provide a continuous indication of the density of the pulp. It is also advantageous, and it is contemplated'by the invention, to provide a pair of spaced electrical contact elements in position to be actuated by the indicator lever whenever the density of the pulp falls below a desired minimum or rises above a desired maximum. The contacts are electrically connected to suitable warning signals. The spacing and actual position of the contacts are both made adjustable so as to adjust both the limits of the pulp density range and the absolute value of the pulp density at which the warning signals are actuated.

A preferred embodiment of the invention, in which the foregoing and other features are incorporated, is shown in the accompanying drawings.

In the-drawings:

Fig. 1 isan elevation of pulp density indicating apparatus constructed in accordance with the invention;

Fig. 2 is an elevation of the vessel in which the pulp is held for density measurement purposes, showing how it may be positioned in an overflowing stream of pulp; and

Fig. 3 is a plan of the vessel shown in Fig. 2.

The new apparatus comprises a vessel 5 in the form of an inverted cone. An inlet opening 6 of ample proportions is formed in its conical wall. A discharge opening is provided at the bottom apex l of the vessel, and the upper edge of the vessel forms an overflow lip 8. Brackets 9 welded to the upper edge of the vessel are provided for mounting it on a suitable supporting frame.

A feed conduit in is secured, as by welding, to the wall of the vessel 5 so that it communicates at its lower end with the interior of the vessel through the inlet opening 6. The upper edge of the feed conduit forms a feed lip II for interposing in an overflowing stream of pulp whose density is to be indicated, issuing, for example, from a launder 12 (Fig. 2). A vertical baiile I3, preferably of somewhat greater width than the feed conduit IEI, extends upwardly between the conduit feed lip H and the vessel overflow lip 8 to a substantial distance above them. The bafile may be simply an upward extension of the wall of the vessel, or it may be a separate element welded or otherwise secured in position to separate the feed lip of the conduit from the discharge lip of the vessel.

In use, the vessel 5 is mounted in position for the feed lip ll of the feed conduit ID to intercept a portion of a stream of pulp overflowing, for example, from the launder 12. The pulp caught within the feed lip is delivered by the conduit through the inlet opening 8 into the interior of the vessel. Although the major portion of the pulp entering the vessel flows downwardly and out through the discharge opening at its bottom apex I, the feed conduit is enough larger than the bottom discharge opening so that more pulp enters the vessel than can leave by this opening. Hence the vessel becomes filled to the top, and excess pulp overflows the overflow lip -8 and flows down the outside of the vessel, to join with the pulp leaving the discharge opening and be caught in a second launder M. This second launder may also receive that portion of the pulp overflowing from the first launder that is not caught in the feed conduit H). The bottom discharge opening of the vessel 5 may be threaded internally to receive standard pipe fittings, if desired, and a valve may be provided to regulate the proportion of pulp passing through the discharge opening to that overflowing at the top of the vessel.

The body of pulp in the Vessel 5 above the inlet opening 6 is substantially quiescent, because it is subjected to no more agitation than results from the upward flow of pulp in excess of the amount that can flow out through the bottom discharge opening. This amount of pulp is considerably less than that which enters through the feed conduit, and in addition the cross sectional area of the vessel above the inlet opening 6 is substantially greater than that of the conduit, so the upward flow of excess pulp is slow and gentle and does not cause sufficient agitation to disturb the substantially quiescent condition of the pulp near the top of the vessel. It is suflicient, however, to keep the solids of the pulp in suspension and to insure that the body of pulp throughout the vessteps are necessary can be taken to bring it back sel is at all times a truly representative sample of the pulp overflowing from thulaunder 12. The short length of the feed conduit l0, and its arrangement on the wall of the vessel 5 so that it is in effect a part of the vessel, contributes to insuring that the pulp sample in the vessel is a representative one. The baflle l3, by preventing pulp splashings from the feed conduit or launder overflow from entering and agitating the body of pulp in the vessel, makes this desirable arrangement of the feed conduit practical. The surface of the quiescent body of pulp in the vessel is of course maintained at a constant level, substantially even with the vessel discharge lip, because the pulp gently flowing up through the vessel freely overflows at this elevation.

It is evident that the body of pulp in the vessel 5 is maintained under excellent condition for determining its density by hydrometer means, and accordingly a hydrometer float I5 is arranged for immersion in the pulp at the top of the vessel. The float is provided with a stem N; which is connected by a doubly pivoted link I! to one end of a density indicating lever l8. The lever I 8 is mounted to swing about a fixed pivot l9, and the stem is guided for vertical movement only by fixed bushings 20. Consequently vertical movement of the float, corresponding to changes of density of the pulp in the vessel 5, is indicated by the free end of the lever [8. This end of the lever may be formed as, or provided with, a pointer 2| which traverses a scale 22 on which pulp density values are inscribed. Thus the lever may be made to give a visual indication of the pulp density at any instant.

It is often desirable to give prompt warning to the plant operating personnel whenever the pulp density rises above, or falls below, a, predetermined maximum or minimum. For this purpose a pair of spaced contact elements in the form of screws 23 and 24 threaded into an insulating yoke 25 are mounted on opposite sides of the free end of the indicating lever 18. The lever itself is provided with an extension 26 which extends between the screws 23 and 24 and forms a cooperating contact element. The yoke 25 carrying the screws 23 and 24 is in turn mounted on a plate 2'! fastened by knurled nuts 28 on screws which pass through an arcuate slot 29 in the plate 30 on which the scale 22 appears.

The lever i8, including its extension contact element 26, and the frame on which it is mounted, are electrically grounded and connected to one terminal of a battery 31 or other electrical power source. The other terminal of the battery is connected to each of twowarning signals, marked High and Low respectively, which may be in the form of colored lights, bells, or other warning devices. One of the contact screws 23 is connected to the other side of the High signal, and the other contact screw 24 is similarly connected to the Low signal.

Whenever the density of the pulp in the vessel 5 falls below a predetermined minimum corresponding to the position at which the contact extension 25 on the lever l8 makes contact with the contact screw 25 connected to the Low" signal, this signal is energized. Similarly, when the pulp density rises to above the desired maximum, contact is made between the extension 26 and the other contact screws 23, and the High signal is energized. In either case, warning is given that the pulp density has reached the minimum or maximum value desired, and whatever within the desired range. The warning signals may, of course, be supplemented, or replaced, with electrically actuated valves by which more or less water is admitted to the pulp, to effect automatic control of its density. Arrangements for accomplishing this result are known and do not constitute part of the present invention.

An important feature of the contact arrangement shown in the drawings is the adiustability of the contact screws 23 and 24. By loosening the nuts 28, the plate 27 with the yoke 25 and contact screws thereon may be moved to any desired position along the density scale. By this adjustment the midpoint between the screws, corresponding to the middle of the density range desired to be maintained, may be pre-sct wherever desired. The contact screws themselves may be screwed in or out in their threaded holes in the yoke 25, and may be locked in the chosen po sition by lock nuts 32, thereby adjusting the spacing between the screws which determine the limits of the density range desired to be maintained. These simple adjustments thus make it possible to pre-select easily both the absolute value of the optimum density to be maintained, and the limits of the density range on either side of this optimum value at which the warning signals are actuated.

I claim:

1. In an ore pulp circuit in which an aqueous pulp of ground ore overflows in a continual stream from one container into another, improved means for indicating the density of the overflowing pulp comprising an indicator vessel in the form of an inverted cone having an inlet opening in the wall thereof, a discharge opening in the downwardly pointing apex thereof, and an overflow lip about the upper edge thereof, a feed conduit mounted on the side of said vessel and communicating at its lower end with the interior thereof through said inlet opening, the upper end of said conduit terminating adjacent the upper edge of the vessel in a feed lip positioned in the path of the overflowing ore pulp, whereby a portion of said overflowing pulp is diverted into said conduit and delivered to the interior of said vessel and is discharged there from in part through the discharge opening at the bottom of the vessel and in part by overflowing the overflow lip thereof, a baffle extending upwardly from between the feed lip of the conduit and the overflow lip of the vessel, and a hydrometer float suspended in the pulp in the upper portion of said vessel.

2. Apparatus for indicating the density of an aqueous pulp comprising a vessel in the form of an inverted cone having an inlet opening in its wall midway between its top and its bottom, a discharge opening at its bottom apex, and an overflow lip about its top periphery, a feed conduit secured to the conical wall of said vessel and having a feed lip at its upper end adjacent the overflow lip of said vessel, said conduit communicating at its lower end with the interior of said vessel through the inlet opening in wall thereof, the discharge opening being sufliciently large with respect to the sizes of the inlet conduit and the inlet opening that the major portion of the pulp entering the vessel flows out of the vessel through it, a substantially vertical baffle extending upwardly between the conduit .eed lip and the vessel overflow lip, said baffle serving to prevent pulp flowing into the conduit from splashing into pulp in upper portion of the vessel, whereby a representative sample body of pulp in the upper portion or" the vessel may be maintained substantially quiescent, and a hydrometer float positioned in the upper portion of said vessel for immersion in such quiescent body of pulp therein.

3. Apparatus for indicating the density of an aqueous pulp comprising a vessel in the form of an inverted cone having an inlet opening in its wall midway between its top and bottom downwardly pointing apex, a discharge opening at its bottom, and an overflow lip about its top periphery, fee-d conduit secured to the conical wall of said vessel and having a feed lip at its upper end adjacent the overflow lip of said vessel, said conduit communicating at its lower end with the interior of said vessel through the inlet opening in the wall thereof, a substantially vertical baffle extending upwardly between the conduit feed lip and the vessel overflow lip, said baffle serving to prevent pulp flowing into the conduit from splashing into the pulp in the upper portion of the vessel, a hydrometer float positioned for immersion in a quiescent body of pulp in the upper portion of said vessel, a pulp density indicating lever actuated by vertical movement of said float, a pair of spaced facing contact elements arranged on opposite sides of said indicating lever in such position that said lever makes contact with one of said contact elements when the pulp density falls to a predetermined minimum and with the other of said contact elements when the pulp density rises to a predetermined maximum, and electrically actuated warning devices connected to said contacts, said contacts being adjustable toward and away from each other to, enable preselection of the limits of the range of pulp density at which the warning signals are actuated, and being adjustable together as to position in the path of travel of the indicating lever to enable preselection of the absolute values of pulp density at which said warning signals are actuated.

WM. WRAITH, JR.

REFERENCES CITED The following references are of record in the 

